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Wednesday, October 19, 2011

Fukushima Daiichi - Emergency Seawater Injection Practice

TEPCO has released a new video, available right now at the APR YouTube Channel. This video shows TEPCO operations during a practice evolution for injecting seawater to a reactor core in an emergency. The video is brief, so a bit of background might be helpful.

TEPCO has been all too well aware since March of this year that there could be a further major earthquake and another tsunami at the Fukushima Daiichi site. To this end, TEPCO has made preparations as much as possible (that is to say, on a basis not to impede or detract from direct recovery work) to respond to another major natural disaster.

For the purpose of the drill in the video just released, then, it is assumed that another earthquake has knocked out the normal water injection cooling at the site and that it cannot be recovered. This would mean a total failure of all of the electric pumps (LOOP) and a failure of diesel generators placed on site to power the cooling and injection systems as they are now. In this eventuality, TEPCO has fire engines and other emergency equipment stationed in safe places, away from danger, which can be moved on site. For the purpose of this drill then TEPCO chooses to directly inject seawater to the reactor core - simulating a last resort to reestablish cooling.

Keep in mind that the location shown in the video for the drill is more toward No. 5 and No. 6 plants at the site. The building enclosure now surrounding No. 1 plant can be seen in the background briefly in a couple of the video shots. TEPCO has constructed an exact duplicate of the water injection manifolds being used on No. 1 through No. 3 plants at this area, complete even to the point of being instrumented. It is with this test rig TEPCO conducts the drill.

Important to note is the statement by TEPCO that only one hour instead of the planned three was required to perform this activity, making it credible that even if loss of normal injection happened at all three plants it might be recovered at all three within three hours of the decision to employ this method.

Seawater injection to the cores was employed for some time during the early period of the Fukushima Daiichi accident, with an effect on materials which will not be known until defueling - but which likely did have an effect in lessening the severity of the accident overall. For those unfamiliar but interested (and with time,) use the Google search box on this site and look for the many early entries I made here during the accident with the word "seawater" and this will become clearer.